This invention relates to plastic bags, and more particularly to a pack of tabless T-shirt bags or merchandise bags, trash bags, and the like made preferably of polyolefins, and method of manufacturing same, which can be used with or without bagging racks and which provide for reliable self-opening of the bags as each bag is removed from the pack of bags.
Since the mid-1980""s, the use of plastic shopping bags has grown dramatically due to the great advantage plastic bags have over bags made of other materials, such as paper. Many types of plastic bags are made of low or high density polyethylene (LDPE and HDPE, respectively), but can be made of any of the polyolefins. LDPE and HDPE bags are stronger, lighter and much more compact to store than paper bags, saving valuable storage space at the merchants"" checkout counter and storage areas. These attributes also make these bags less expensive to transport. LDPE and HDPE bags can be manufactured and sold at a fraction of the cost of competing paper bags, making them the bags of choice for merchants. LDPE and HDPE bags are also actually more environmentally friendly than paper bags since they require about 70 percent less energy to manufacture than competing paper bags and are readily recyclable, and when not recycled, are non-toxic when incinerated or disposed of in landfills.
Many groceries stores and other merchants now use a style of plastic bag to bag groceries and other merchandise commonly referred to as T-shirt bags. T-shirt bags are pleated bags which are closed, by heat sealing, at a bottom edge, and have a pair of integral loop handles extending upwardly to define an open mouth of the bag therebetween. T-shirt bags usually have a central tab that extends from front and rear walls of the bag. Each of the front and rear walls have a central tab that extends from the walls, respectively. The central tabs have aligned apertures into which bagging racks are received.
Because high density polyethylene (HDPE) has a greater resistance to stretching and deformation than LDPE plastic, HDPE plastic is generally used for making T-shirt bags, although LDPE and other polyolefins can also be used. T-shirt bags are normally provided in packs of aligned bags and these packs of bags are usually used in conjunction with bagging racks.
T-shirt bags are generally manufactured using a continuous tube of HDPE plastic, or other plastic material having the desired color, thickness, and diameter, formed on a extrusion machine. The continuous plastic tube is passed over rollers to roll the continuous plastic tube onto a spool.
The newly formed continuous plastic tube is usually subjected to corona surface treatment, if the bags to be formed from the continuous tube of HDPE are to be printed on one or both sides. It has been found that corona surface treatment, or other known methods to electrically and chemically change the entire outer surface of the continuous plastic tube, contributes somewhat to the self-opening feature of applicants"" plastic bag pack system.
After being corona surface treated and rolled (if the bags might be printed), the roll of continuous plastic tube is unrolled and pleated on a pleating machine. A bagging machine then heat seams and cuts sections of the pleated tube at top and bottom edges to form closed and flattened pleated bags of a desired length and width, with the pleated sides being at both sides of the flattened pleated bags. These sections are often referred to as pillowcases. The pillowcases are eventually stacked in aligned stacks.
Thereafter, hydraulic die cutting or other cutting methods are utilized to remove material at the stacked pillowcases"" upper portions to form the handles and tab portions. Each loop handle has four layers of plastic material since they are cut out from the pleated side portions of the bag.
Despite the many advantages HDPE T-shirt bags have over paper bags, they are not self-standing like thicker and stiffer paper bags with a discreet flat bottom. This is due to their relatively thin and flexible material. In grocery stores settings, where quick and easy loading of bags is desirable, packs of T-shirt bags are generally supported on a bagging rack as merchandise is loaded into the bags to overcome the lack a of self-standing ability.
The packs of T-shirt bags suffer from drawbacks. Prominent among these drawbacks include the lack of a convenient and easy to manufacture self-opening feature, to eliminate the need for the box person to struggle to open up each bag in the pack of bags.
In order to prepare a T-shirt bag for loading with merchandise, it is desired that only the first layer of the bag material of the top bag are pulled away from the pack, thereby opening just the top bag. Since the HDPE material is very thin, typically between 0.5 and 1 mil thick (0.0005 and 0.001 inches), it is sometimes difficult for the checkout clerk or box person to grasp just the top layer of bag material. One can often see a sponge or source of tacky material, such as a glue stick, retained at the top of bagging racks, with which the checkout clerk or box person can dampen his or her fingers to aid in grasping just the top layer of material of the bag. However, this takes additional time and effort in the bagging process. This cycle has to be repeated with each successive bag to be loaded.
In addition, the bag packs systems typically leave waste xe2x80x9cbooksxe2x80x9d of heat bonded central tabs on the bagging rack. These books accumulate on the bagging rack and are generally thrown out. In those styles of packs of bags which employ a central tab slit through their central tabs for mounting the pack of bags on a tab receiving hook of a bagging rack, it is sometimes difficult to engage the slitted central tab with the tab receiving hook.
There are also so-called xe2x80x9ctablessxe2x80x9d designs, in which no portion of the bag is left on the bagging rack. In these bag designs, each bag will tear through a suspension aperture completely as each bag is removed.
Existing tabless bag designs that are provided with a self-opening feature utilized frangible bonding to cause each bag to open. However, use of frangible bonding as a self-opening feature can be problematic because the strength of the bond formed depends on several factors, including the thickness of the plastic film, the degree of corona treatment, the size and shape of the die used to form the areas of frangible bonding, the pressure applied to the dies, and static changes in the bag materials. While adhesive have been used to create a self-opening feature in tabbed bag designs, use of adhesive in a flapless design is unknown to the inventor. Use of adhesive in the central tabs of packs of bags would be particularly useful to assure self-opening inasmuch as a pulling force close to the tearing slit will ensure that the bag will reliably open.
It is desirable to have a pack of plastic bags which can be easily manufactured, yet which provides for reliable self-opening of each bag of the pack of bags, does not leave a book of plastic tabs on the bagging rack, can be easily placed on a bagging rack, and does not tear the lower portion of the bag.
A pack of self-opening plastic bags for use with a bagging rack has a mouth for receipt of merchandise. Each plastic bag in the pack of bags has a mouth tab portion between its two upwardly extending handles. The mouth tab portions extend from front and rear walls along sides of the mouth. Through the stack of bag, in the mouth tab portion is a curved aperture slit for receiving a bagging pack hook member of a bagging rack. The curved aperture slit has a main cut section that is substantially parallel with the bottom edges of the walls, and two curved end sections at respective ends of the main cut section. One end section curves towards a top edge of the tab portion, and another end section curves in an opposite direction and wraps back under the main section until it is substantially perpendicular to and adjacent the main cut section. In one embodiment, the first curved section is dashed.
Contact adhesive bonding is preferably utilized near the curved aperture slit. The handles also have holes for use in suspending the pack of self-opening bags on the bagging rack. Due to the adhesive bonding between adjacent bags, as an outermost bag is removed from the pack of bags on the bagging rack, the next adjacent bag in the pack of bags automatically self-opens into an open position for loading with merchandise.